Quaife ATB Limited Slip Differential Retrofit - F2x M140i M240i

The Quaife ATB (Automatic Torque Biasing) differential is a unique type of limited-slip diff that substantially improves traction for powerful vehicles using only gear mechanisms. This clever design revolutionised the differential market - offering a superior level of performance and warranties compared to its competitors.

In 2007, BMW began welding the crown wheel gear to the open differential instead of bolting them together. This means for models such as the F20 M140i and F22 F23 M240i we must now machine the crown wheel gear off, and drill it so that a Quaife ATB LSD can be bolted on in the open differential's place. This is specialist work that we get done. We offer two methods of upgrading - you can send up your differential for the retrofit to be performed or we offer an exchange program whereby we send you a pre-built differential with the Quaife ATB unit already inside.

An Exchange Quaife Limited Slip Differential is a complete BMW differential equipped with a Quaife ATB LSD. We offer these in exchange for your original differential so that you avoid the lengthy downtime and complications of a Quaife ATB installation. However, this is only offered to you if your vehicle has done less than 60,000kms and if it's done more you will need to send your differential in for conversion. BM Performance guarantees the Exchange Quaife Limited Slip Differentials for 2 years, and the Quaife ATB itself comes with a limited lifetime warranty. The total cost is inclusive of delivery of the Exchange Quaife Limited Slip Differential and the return of your standard unit.
 
The Exchange Quaife LSD unit is also sold with an additional $500 core charge (not included in the purchase price). We will send you an invoice for this charge once your pre-built exchange differential is prepared and ready to send.  This amount will then be refunded upon the return of your standard differential to us in good working order.

Exchange Quaife Limited Slip Differentials are only available for certain models. If we don't have any exchange differential available to suit your car you will need to send us your differential for retrofitting.

If your BMW has done more than 60,000kms or if you would prefer to have your own differential retrofitted with the Quaife ATB unit you can send it to us for converting. Depending on your location, the process can take 20 days including freight transit time. The cost is also fully inclusive of freight to bring your standard differential to us and the return. All you need to do is organise the removal of your differential (at your own cost).

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All standard BMW models come from the factory fitted with the basic "open differential" - a simple device that allows the driving wheels to turn at different speeds (enabling the car to navigate around corners). The problem with the open diff is that it can only ever apply the same amount of torque to both driving wheels, so when a wheel slips, it will only put through the amount of torque it requires to power that spinning wheel (very little!). The car spins away power in these instances.

Additionally, BMW use various electronic traction systems that "curb" power to the drive wheels during traction loss (indicated by the flashing traction light on your dashboard). The Dynamic Stability Control system (DSC) is designed to "curb the engine output and stop slip on the wheels", a good feature in theory, but is still in its early stages of development and is way too intrusive, often frustrating the driver when trying to push on. If you accelerate hard from slow speeds, or try to power out of turns (especially in slippery conditions), the loss of traction will make the engine sap power away from the wheels. Turbocharged rear-wheel drive cars with high torque outputs suffer the most, such as BMW's M135i, and conditions are worsened by the fact they are equipped with run-flat tyres and stiff suspensions. Of course if you are lucky enough to have sufficiently deep pockets, all BMW M-Powers come from the factory with a mechanical limited-slip differential, demonstrating that even BMW themselves know that powerful cars need these important devices.

Fortunately, there are clever differentials out there on the aftermarket that will transfer torque to the wheel with more traction rather than take it away... 

The Quaife unit uses sets of floating helical cut gear pinions that run in pockets and mesh during normal driving, acting as an open diff. Should one of the driving wheels start to spin however, the helical gears start to generate a torque bias thanks to the axial and radial thrust of the helical gear pinions in their pockets. The result is an instantaneous and progressive transfer of torque away from the spinning wheel to the one with more traction, always varying accordingly and automatically.

With the DSC and traction systems switched off during traction loss, you will feel the Quaife transferring the power to the wheel with more grip in a smooth and predictable manner. Any movement at the rear end is controlled and intuitive for the driver. With the traction systems switched on, you will rarely ever see the light flicker on your dashboard as the Quaife allows you to power through any loss of traction, working in perfect harmony with all of the BMW's standard equipment.

The car ultimately becomes easier to control and is able to apply its power to the tarmac with maximum effect. Acceleration, cornering speeds, handling, steering, and overall dynamics of the car are dramatically improved! The Quaife is capable of varying the torque split from 0-80%, and does this quietly and smoothly in operation. It does not affect any of the traction systems on the car, and does not affect the manufacturer's warranty. All backed by its own worldwide lifetime guarantee.

How is the Quaife ATB superior?

• requires no servicing or maintenance.
• is silent and smooth in operation.
• is guaranteed to work seamlessly with all electronics and OE components.
• uses a progressive, non-locking helical gear design - allowing for safe and predictable control during moments of oversteer.
• is capable of biasing up to 80% of torque to wheel with most grip.
• comes with a limited lifetime warranty.

The clutch-plate problem

The Quaife solution

What is the Quaife warranty?

Will the Quaife ATB affect my new car warranty?

Key features

• Manufactured in Great Britain
• Precision manufactured from certified steel billets and inspected to ISO9001-2008 standards
• Direct replacement for factory standard open differential unit (no 'shims' required)
• Uses regular gear oil lubrications systems and maintenance schedule
• Has been consistently tested and improved since its launch in the 1980's
  

PLEASE LET US KNOW IF IT IS AN AUTO OR MANUAL CAR